refactor: settings format picker redesign with Audio/Video sub-pickers, fix delete routing

- Replace Type/Quality settings with single Format button -> Audio/Video sub-pickers
- Each sub-picker shows format options (bitrates for audio, resolutions for video)
- Replace DefaultQuality with DefaultAudioFormat/DefaultVideoFormat in UserPreferences
- Add DB migration 002 for new preference columns
- Update repo layer SQL queries for new schema
- Update playlist flow to use new preference fields
- Fix missing deleteaccount and delaccount_ callback routing
- Add back_format routing for format picker navigation

internal/handler/handler.go

@@ -232,6 +232,9 @@ func (h *Handler) HandleCallback(ctx context.Context, cb *models.CallbackQuery)
 		h.answerCb(ctx, cb.ID)
 	case data == "history":
 		h.historyCallback(ctx, chatID, msgID, cb.ID, userID)
+	case data == "deleteaccount":
+		h.deleteAccountPrompt(ctx, chatID, msgID, userID)
+		h.answerCb(ctx, cb.ID)
 	case data == "pending_cancel":
 		h.backToMenu(ctx, chatID, msgID, cb.ID, userID)
 	default:
@@ -259,6 +262,12 @@ func (h *Handler) routePrefixedCallback(ctx context.Context, chatID int64, msgID
 		h.handlePlaylistSelectAll(ctx, chatID, msgID, userID)
 	case data == "pl_confirm":
 		h.handlePlaylistConfirm(ctx, chatID, msgID, userID)
+	case strings.HasPrefix(data, "delaccount_"):
+		if uid, err := strconv.ParseInt(data[11:], 10, 64); err == nil && uid > 0 {
+			h.deleteAccountConfirm(ctx, chatID, msgID, uid)
+		}
+	case data == "back_format":
+		h.handleSettingsSelection(ctx, chatID, msgID, userID, "format")
 	case data == "back_settings":
 		h.backToSettings(ctx, chatID, msgID, userID)
 	case strings.HasPrefix(data, "settings_set_"):